Beta-dimethylaminoethyl ester of para-butylamino-benzoic acid



Patented Nov. 29, 1932 STATES PATENT orrca OTTO EISLEB, OF HOFHEIM-ON-TA'UNUS, GERMANY, ASSIGNDR 'lO WINTHROP CHEM- ICAL COMPANY, 11530.,015 NEVJ YORK, H. Y., A CQRPOR-ATION OF NEW YORK IBETA-DIMETHYLAMINOETHYL ESTER (3F PARA-BUTYLAMINO-BENZOIG ACID No Drawing. Application filed June 22, 1332, Serial No. 618,811, and at Switzerland December 1930.

My present invention relates to the betadimethylaminoethyl ester of para-butylaminobenzoic acid, which compound has the following probable constitution:

In U. S. Patent No. 1,550,350 of August 18, 1925, are described alkamine esters of N- monoalkylated and N-monoalkoxy-alkylated derivatives of para-aminobenzoic acid, which are obtained by esterifying, by one of the usual methods, para-Nr-monoalkylor para- N monoalkyloxyalkylaminobenzoic acids, other than para-N-monomethyland para- N-monoethylaminobenzoic acid by means of amino alcohols or by treating alkamine esters of para-aminobenzoic acid with such alkylating or alkoxyalkylating agents as contain alkyl residues or alkoxyalkyl residues having more than 2 carbon atoms.

Now I have found that the hitherto unknown beta-dimethylaminoethyl ester of para-butylaminobenzoic acid, which is by far superior to the analogous products hitherto known and especially to those described in the said U. S. patent, is obtained by esterifying para-butylaminobenzoic acid with betadimethylaminoethanol according to. one of the usual methods, or by treating with a butylating agent the beta-dimethylaminoethyl ester of para-aminobenzoic acid.

The new product itself and its water-soluble salts, for instance, the monohydrochloride, have a very strong anaesthetising action without causing any irritation and have a very favorable thereapeutic index. The therapeutic index, i. e. the relation between the efiicacy and the toxicity of a therapeutic shows the value of a therapeutic substance. The therapeutic index of the new product is remarkably greater (up to two and four times greater) than that of the known analogous products, as for instance described in U. S. Patent No. 1,550,350. The

new product, which has a good stability, also in aqueous solutions is, therefore, of a greater usefulness for anaesthetic purposes, especially for anaesthesia of the mucous membranes and for nerve anaesthesia (conductive anaethesia) than the known products. The new product is also suitable" for 'lumbaranaes- 1 thesia and sacral anaesthesia.

The following examples illustrate the'invention. (-1) -butylaminobenzoic acid is produced by boiling an aqueous solution of the sodium salt of l-aminobenzoic acid with N-butyl-bromide. It forms a colorless crys talline powder melting at 153 0:154 C.

Equimolecular quantities of l-butylaminobenzoic acid and the hydrochloride of betadimethylaminoethanol are suspended in 10 times their joint weight of toluene; the mixture is saturated with hydrochloric acid gas and heated in an oil bath at about 150. C. while a current of hydrochloric acid gasis slowly passed through the mixture so that toluene slowly distils. Along with toluene the water produced by the esterification distils. After heating for about'lO hours the mixture is cooled and water is added until the salt is dissolved; the layer of tolueneis separated and, the ester base precipitated from the aqueous solution by means of a solution of sodium carbonate. By dissolving the base in etherfd'rying the ether solution separated over potassium carbonate and adding alcoholic hydrochloric. acidto the solution v until it is neutral to litmus, the monohydroat 43 C. The picrate melts at 120 C.

When treated with oxalic acid, the base forms 'a neutral oxalate which is easily soluble in water and an acid oxalate which is very diflicultly soluble in cold water. The mononii the ether.

gate forms lamellae and melts at 131 C.132

(2) 4-butylaminobenzoic acid ethyl ester is produced by boiling, in a reflux apparatus, 4i-butylaminobenzoio acid and 4 times the quantity of alcohol containing 1 mol of hydrogen chloride, partly distilling the alcohol and decomposing by means of caustic soda solution. It forms colorless crystals and melts at 69 C.70 C.

By boiling t-butylaminobenzoic acid ethyl ester with an excess of beta-dimethylaminoethanol, while adding a small quantity of sodium ethylate, the alykl is eliminated; ethyl alcohol distils; after the excess of dimethyliling the excess of ethylene chlorohydrin in a vacuum. The oily crude ester is purified by dissolving in ether, washing free from acid with a solution of sodium carbonate, drying over potassium carbonate and distilling The purified ester melts at 64 (ll-65 C.

4-butylaminobenzoic acid-beta-chlorethylester is dissolved, while cooling, ina benzene solution of somewhat more than the calculatedquantity of dimethylamine; this solution isheated in a pressure vessel for8 hours at C. After cooling the benzene solution is several times shaken with water,'whereby the dimethylamine salt is dissolved in water,

but the ester base remains in the benzene layer. The ester base is eliminated from the benzene layer by shaking with dilute acetic acid; the base is precipitated from the acetic acid solution by means of caustic soda solution, dissolved in ether and dried over sodium carbonate. By precipitating the ether solution with alcoholic hydrochloric acid until it is neutral to litmus, the 4-butylaminobenzoic acid-beta -dimethylaminoethylestermonohydrochloride is obtained; it melts at 147 'C-148 C.

(4) Equimolecular quantities of l-aminobenzoic acid beta-dimethylaminoethylester and N-butyl bromide and butyl alcohol as diluent are refluxed for 3 hoursin an oil bath. Hot water is then added and the butyl alcohol is distilled with steam. After cooling the aqueous solution is precipitated with sodium carbonate solution, the alkamineester mixsium carbonate, and, after the ether has been distilled, fractionated in a vacuum. The 4- butylaminobenzoic acid-beta-dimenthylaminoethylester distils at 210 C. under 4. mm. pressure. For completely purifying, the monohydrochloride is produced in an alcoholic solution; it melts at 147 C.148 C.

I claim:

The beta-dimethylaminoethylester of parabutylaminobenzoic acid, which compound has the following probable constitution I IH(OH2)aOH and forms colorless crystals melting at 48C., said compound forming a monohydrochloride being a colorless crystalline powder, easily soluble in Water and melting at 147 (1-148 C. and a mononitrate melting at 131 C.-132 G.

In testimony whereof, I affix my si nature. 0

OTTO EISLEB.

ture is dissolved in ether, dried over potas- 

